1. Field of the Invention
The present invention relate to an access device for preventing transmission of copyrighted contents to an external network and a method for the same, and more particularly, to an access device for preventing transmission of copyrighted contents to an external network and a method for the same, in which the copyrighted contents downloaded to a device connected to a home network are prevented from being shared with unauthorized users connected to the external network, while the downloaded contents can be freely shared between authorized users connected to the home network.
2. Description of the Related Art
In the related art, web content providers provide copyrighted contents based on paid subscription and limits (or prevents) the contents from being shared with unauthorized users. To protect various audiovisual (AV) contents such as internet broadcasts, images, and MP3 music files, transmission of contents to unauthorized users is blocked by using various related art methods such as a conditional access system (CAS). In such a method for protecting copyrighted contents, contents can only be played in a specified device, transmission of contents is prohibited even within a home network, or contents are often prohibited from being stored on a device. In such cases, there is a considerable limitation in sharing or playing the web contents on a private home network. This adversely affects AV home-network business from the standpoint of both the consumers and service providers. To overcome such a limitation, a digital transmission content protection over Internet Protocol (DTCP over IP) method has been suggested.
FIG. 1 illustrates a packet transmission flow in a related art home network that employs DTCP over IP.
DTCP over IP is one of methods that enable transmission and play of copyrighted contents in a certain areas such as a home network. More specifically, DTCP over IP restricts transmission of packets having a header indicated with a time-to-live (TTL) value of “3”, or restricts a round-trip time (RTT) of packets to 7 ms, so the area to which packets can be transmitted is restricted to a home network.
The packet transmission procedure of DTCP over IP will be described with reference to FIG. 1. When a device 1 transmits packets of copyrighted content to a device 2 through an access device 30, the TTL value of the packets is set to “3” at the start of transmission. Then, when the packets are transmitted from the device 1 to the access device 30, the TTL value of the packet is reduced to “2”. Here, since the TTL value is greater than “0”, transmission from the access device 30 to the device 2 is allowed and the TTL value is then reduced to “1”. Therefore, transmission 10 of copyrighted content packets from the device 1 to the device 2 through the access device 30 is allowed.
Similarly, in the case of an external network, when the device 1 transmits content protected packets, i.e., copyrighted content packets, to a device 50 connected to an external network, transmission 20 from the device 1 to the access device 30 is allowed and the TTL value is then reduced to “2”. Again, since the TTL value is greater than “0”, packet transmission 40 from the access device 30 to the device 50 connected to the external network is allowed and the TTL value is reduced to “1”. Therefore, packet transmission from the device 1 to the device 50 connected to the external network is also allowed.
As described above, when the related art DTCP over IP method is used, there is at least one problem in that the content protected packets may be transmitted to a network connecting apartment complex or to devices outside a home network, which may be connected to the same access network as the home network.
When implementing the DTCP over IP method, transmission of copyrighted content packets to external network still cannot be prevented under the related art standard in which the TTL value of the content protected packet is set to “3”, and as a result, the policy that permits the copyrighted contents to be shared only within the authorized home network is often violated. More specifically, the copyrighted content packets in which the TTL value is set to “3” may be transmitted to devices of the external network through an access device such as a gateway that connects the home network with the external network.
The related art methods implementing DTCP over IP have an advantage in that subscribers can freely transmit/share or play copyrighted contents within a home network. However, there is a drawback in that the contents may be transmitted to unauthorized external network.